Stabilized polyester compositions and monofilaments thereof for use in papermachine clothing and other industrial fabrics

ABSTRACT

A polyester composition comprising from 90 to 97% by weight of at least one polyester derived from the condensation of 1,4-cyclohexane dimethanol and at least one dicarboxylic acid or an ester thereof, from 0.1 to 5% by weight of at least one primary anti-oxidant defined as an alkyl and/or alkyl peroxy radical scavenger, from 0.1 to 5% by weight of at least one secondary anti-oxidant defined as a compound capable of decomposing a hydroperoxide, from 1 to 4% by weight of at least one polyamide terpolymer. Utility of such a composition includes use in a monofilament yarn or fiber, use in a papermachine clothing including such a monofilament yarn or fiber and/or including the polyester composition.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of PCT application No. PCT/IBO2/03292,entitled “STABILISED POLYESTER COMPOSITIONS AND MONOFILAMENTS THEREOFFOR USE IN PAPERMACHINE CLOTHING AND OTHER INDUSTRIAL FABRICS”, filedJul. 19, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention.

[0003] The present invention relates to stabilized polyestercompositions and monofilaments thereof for use in papermachine clothingand other industrial fabrics.

[0004] 2. Description of the Related Art.

[0005] Monofilaments manufactured from polyethylene terephthalate (orPET) are used extensively in the production of papermachine clothing andother industrial fabrics. A paper machine typically includes threesections. In the forming section, where the cellulosic fibers arepresented to a forming fabric in the form of a slurry, the fabrics arepredominantly constructed from polyester monofilaments, morespecifically PET. In the forming section of the papermachine thetemperature rarely exceeds 60° C. and the fabric is subjected to severewear from suction boxes used to withdraw water from the paper web, suchthat the fabric life is seldom over 120 days. The paper sheet istransferred from the forming section into the press section of thepapermachine and at this point the solids content of the slurry isapproximately 20%. Here, the paper sheet passes through a series of niprolls or shoe presses, and due to the need for resilience, polyamideshave been the material of choice. The paper sheet has about 40% solidscontent as it is transferred from the press section into the dryersection of the papermachine.

[0006] In the dryer section, a textile fabric holds the paper sheetagainst steam-heated cylinders. The temperature of the cylinder surfacecan exceed 120° C. and the evaporation of water from the sheet ensuresthat the relative humidity remains at 100%. Fabrics composed of PET areconventionally used for most dryer fabric applications. However, towardsthe end of the paper machine, as the solids content approaches 80 to90%, the cooling effect of the evaporation is reduced and thetemperature to which the fabric is actually exposed increases such thatthe PET fabric is now subjected to significant degradation. In mostapplications, the life of a typical PET fabric can be in excess of 12months. However, under these extreme conditions service life is reducedsignificantly.

[0007] In order to extend the service life of dryer fabrics exposed tothese conditions, suppliers to the industry have used an array ofmaterials as the constituent material of the dryer fabric. Polyphenylenesulphide (or PPS) provides excellent thermal, hydrolytic and oxidativestability. However, the PPS polymer is significantly more expensive thanPET. Monofilament extrusion of PPS is more problematic, leading to ahigher percentage of product rejections and therefore higher productioncosts.

[0008] Copolyesters derived from 1,4-cyclohexane dimethanol,terephthalic acid, isophthalic acid and esters thereof, have beensuggested as a cheaper alternative. U.S. Pat. No. 5,169,499 teaches theuse of such copolyesters to improve the hydrolytic stability ofpapermachine clothing. The large cyclohexane moiety present in thepolymer backbone serves to provide steric hindrance to the hydrolyticcleavage of the ester bond. However, the cyclohexane ring also serves toincrease the susceptibility of such polyesters to oxidative degradation.It is generally accepted that the oxidation of polymers follows a freeradical chain reaction mechanism that is initiated by abstraction of ahydrogen atom from the polymer, forming an alkyl radical. This alkylradical can very quickly react with oxygen to form an alkyl peroxyradical, which propagates additional reactions. Each cyclohexane ring,whilst providing steric hindrance, also introduces two tertiary hydrogenatoms into the backbone of the polymer; that is two hydrogen atoms thatare each bonded to a tertiary carbon. Due to the effects of electronwithdrawal, the carbon hydrogen bond strength is reduced, such that theabstraction of these hydrogen atoms is much more likely at elevatedtemperatures. Hence, polyesters that contain this type of cyclohexanemoiety are more prone to oxidative degradation than PET which has notertiary hydrogen atoms in its polymer backbone.

[0009] The art of stabilizing polymers to oxidation at elevatedtemperatures is extensive. U.S. Pat. No. 5,763,512 teaches the use of acombination of a sterically hindered phenol and a specific organicphosphite for the stabilization of polyamides, polyesters or polyketonesagainst oxidative, thermal and/or light induced degradation. Stericallyhindered phenols and other organic compounds that can formresonance-stabilized radicals, are known to scavenge alkyl and alkylperoxy radicals formed during the oxidation of a polymer, and arecommonly termed primary anti-oxidants. Tri-aryl phosphites and thioestercompounds react with hydroperoxide moieties formed during oxidation, andare commonly referred to as secondary anti-oxidants. Polymer Science andEngineering, Vol. 30, No. 17, page 1041 by A. Aurebach et al. citedherein, describes blends of PCT and the use of certain anti-oxidants toimprove melt stability.

[0010] U.S. Pat. No. 5,981,062 attempts to improve the stability of suchpolyesters through blending with polyamides, more specifically theblending of polyesters based upon a polyhydric alcohol of1,4-cyclohexane dimethanol with 5 to 20% of a polyamide, preferablyPA66. The blends are shown to improve the oxidative and hydrolyticstability of monofilaments manufactured therefrom.

[0011] Polyamide 66 is known to form gels if held at elevatedtemperatures for an extended period of time (see Nylon handbookpublished by Hanser/Gardner Publications 1995, Chapter 3, Page 55).Polyesters derived from 1,4-cyclohexane dimethanol and terephthalic acid(or its esters); i.e. PCT, or polyesters derived from 1,4-cyclohexanedimethanol and terephthalic and isophthalic acid (or their esters); i.e.PCTA, have melting points of 295° C. and 285° C. respectively. Thesehigh melting points necessitate high temperature processing and melttemperatures which can be in excess of 300° C. We have seen that thiswill lead to some degree of gel formation with polyamide 66 and canresult in some thermal degradation of PA6. Gels occur during meltprocessing when cross-links form between individual polymer chains. Inmonofilament extrusion, the presence of gels leads to diameter variationat localized sections of the filaments that are very brittle and exhibitpoor mechanical properties. It is known that these filaments break underthe normal loads experienced in a weaving process. Such filaments are ofan unacceptable quality.

[0012] It is known to those skilled in the art that polyesters andpolyamides are generally incompatible, and tend to exhibit phaseseparation in the melt. Phase separation induces micro-voids and variousstructural defects, the effect of which is to introduce weak pointsobserved as tenacity variation along the length of the monofilament.These defects can also affect the drawing process, reducing theefficiency of monofilament manufacture.

[0013] In addition, the blends alone do not provide sufficient oxidativestability to match that of the industry standard polyester, PET,ensuring that they, and the monofilaments and textile structures derivedfrom them, cannot be used universally. What is needed in the art isfurther stabilization of such polyesters, as described herein, againstthermo-oxidative degradation. Textile structures formed from suchmonofilaments may be woven for a plurality of said filaments, or theymay be constructed from helical spiral coils of the monofilaments linkedtogether by pintle yarns, a process that is described in U.S. Pat. No.4,423,543.

SUMMARY OF THE INVENTION

[0014] The present invention provides a PCTA copolymer for use inpapermachine clothing and/or other industrial fabrics, having good dryheat and hydrolysis resistance.

[0015] According to a first aspect of the present invention there isprovided a polyester composition comprising from 90 to 97% by weight ofat least one polyester derived from the condensation of 1,4-cyclohexanedimethanol and at least one dicarboxylic acid or an ester thereof, from0.1 to 5% of at least one primary anti-oxidant defined as an alkyland/or alkyl peroxy radical scavenger, from 0.1 to 5% of at least onesecondary anti-oxidant defined as a compound capable of decomposing ahydroperoxide, from 1 to 4% of at least one polyamide terpolymer.

[0016] The composition further preferably comprises from 0.5 to 2% of atleast one hydrolysis stabilizer.

[0017] According to a second, aspect of the present invention there isprovided an article of papermachine clothing comprising the polyestercomposition of the aforesaid first aspect of the invention.

[0018] According to a third aspect of the present invention there isprovided a monofilament comprising the polyester composition of thefirst aspect of the invention.

[0019] The polymer compositions of the present invention exhibitcomparable resistance to thermo-oxidative degradation to standard PETand vastly superior hydrolytic degradation, particularly at elevatedtemperatures, and improved property uniformity. Consequently the polymercompositions of the present invention may be processed using standardequipment with consistent properties.

[0020] The polyester compositions (which term as used herein includescopolyesters) of the present invention are those containing acyclohexane moiety in the polymer backbone. The polyester preferablyincludes the condensation product of 1,4-cyclohexane dimethanol andterephthalic acid and/or an ester derivative of terephthalic acid.Ideally the polyester includes the condensation product of1,4-cyclohexane dimethanol terephthalic and isophthalic acids and/ortheir ester derivatives. Suitable commercially available polyesters arethose available from Eastman Chemical Co., of Kingsport Tenn. under thetrade marks THERMX 3879 for PCT and THERMX 13319 for PCTA respectively.

[0021] The primary anti-oxidant may include from 0.1 to 5% by weight ofthe blend, and the secondary anti-oxidant may include from 0.1 to 5% byweight of the blend. The term “primary anti-oxidant” refers to amaterial that by way of its chemical composition can readily react withalkyl peroxy radicals forming more stable radicals that do not furtherpropagate the chain reaction. These radicals can undergo furtherreaction with additional radicals to prevent them from propagating theoxidation chain. The most efficient primary anti-oxidants, by way ofthis reaction, are regenerated. The term “secondary anti-oxidant” refersto a class of additives that by way of their chemical composition canreact with hydro-peroxide moieties formed as a result of the oxidationof a polymer, thus neutralizing these highly reactive species. Detailsof mechanisms involved in preventing oxidation are included in “PlasticsAdditives. Chapter 1 published by Hanser (1993)”. The primaryanti-oxidant is preferably a hindered phenolic compound.

[0022] The type of primary anti-oxidant described in this art isexemplified by, but not limited to the following:

[0023] The phenolic anti-oxidant illustrated above, i.e. pentaerythrityl(tetrakis-3-(3,5-di-tert.-butyl-4-hydroxy phenyl) propionate), CASNumber 6683-19-8, is sold under the trade name IRGANOX 1010 by CibaCorporation.

[0024] The secondary anti-oxidant is preferably a phosphite. The type ofsecondary anti-oxidant described in this art is exemplified by, but notlimited to the following:

[0025] The phosphite secondary anti-oxidant illustrated above; i.e.Bis(2,4-dicumylphenyl)pentaerythritol diphosphite, CAS No. 154862-43-8,is sold under the trade name DOVERPHOS® S-9228 by Dover Chemicals,Dover, Ohio.

[0026] The hydrolysis stabilizer added to the blend was chosen for itsability to neutralize the carboxyl end groups of the polyester and isadded in quantities to minimize the problems associated withmanufacturing monofilaments from the blend. The composition may includethe hydrolysis stabilizer in an amount from 0.5 to 2% by weight. Thepreferred stabilizer is exemplified by, but not limited to, the class ofcompounds known as carbodiimides. These compounds may be used in themonomeric or polymeric forms. A specific example of this type ofstabilizer is 2,6 diisopropylphenyl carbodiimide which is supplied underthe trade name of STABAXOL I by Rhein Chemie GmbH.

[0027] The polyamide terpolymer stabilizer ideally has a melting pointin the range from 120° C. to 220° C. The terpolymer is added such thatit includes from 1 to 4% by weight of the blend. An example of such aterpolymer is sold commercially by Du Pont de Nemours under the tradename ELVAMIDE 8063. The term “terpolymer” as used herein refers to apolymer composed from more than two distinct repeat units as opposed toa homopolymer with one, and a copolymer with two. For example, apolyamide terpolymer may be composed of three or more repeat units suchas 6, 6,6, 11 and 12. The type and ratio of the components has asignificant influence upon the properties of the material, such thatthey are useful. The term “polyamide” refers to any of the knownpolyamides, which through polymerization, can be formed intoterpolymers. Examples include, but are not limited to polyamide 6,polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,9, polyamide6,10, polyamide 6,12.

[0028] The blend of a polyamide terpolymer, a primary anti-oxidant and asecondary anti-oxidant as defined herein combine synergistically toprovide a significant improvement in the ability of the polyestersdescribed to withstand oxidation at elevated temperatures. Furthermorethe additives in the composition of the present invention have highcompatibility to the main resin, unlike many prior art compositions,resulting in the compositions of the present invention having uniformproperties including color, tensile properties and resistance todegradation.

[0029] The polyester composition blends of the present invention provideimproved melt extrusion and consequently the consistency ofmonofilaments produced by such extrusion is improved.

[0030] An extrusion processing aid in the form of a lubricant, such assilicone, may be added to the blend, and can include between 0.1 and 1%by weight of the final composition.

[0031] The polyester compositions of the present invention areparticularly useful as papermachine clothing or other industrial fabricswhere the textile is likely to be exposed to elevated temperatures inthe presence of water or otherwise high levels of humidity areanticipated. Such fabrics may be woven from a plurality of filaments orformed from many spiral coils linked together in a construction commonlytermed a spiral fabric and described in U.S. Pat. No. 4,423,543.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

[0033]FIG. 1 is a graph of tensile strength retention as a function oftime, illustrating the hydrolysis resistance of one example of thepresent invention compared with PET and PCTA. The hydrolysis test wasperformed as outlined in example 2; and

[0034]FIG. 2 is a graph of tensile strength retention as a function oftime illustrating, the thermo-oxidative stability of one example of theinvention compared with PET and PCTA. The oven-aging test was performedas outlined in Example 2.

[0035] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate one preferred embodiment of the invention, in one form, andsuch exemplifications are not to be construed as limiting the scope ofthe invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The hydrolysis and oven aging resistance of a composition inaccordance with the present invention were compared to that of astabilized PET formulation, representing the industrial standard. Also,the hydrolysis and oven aging performance of the PCTA formulationreported in U.S. Pat. No. 5,981,062 was included for comparison.

EXAMPLE 1

[0037] In the following example, a comparison of the stabilizers thatcan be used is described, and their effect on the oxidative degradationof the monofilament outlined. The components in each sample werepre-blended, and then dried at 170° F. for 15 hours. Monofilamentextrusion was carried out on a 1″ single screw extruder with an L/Dratio of 25:1. The resins were gravity fed into the extruder from ahopper, into which a positive pressure of nitrogen gas was maintained toprevent moisture ingress. The composition of the samples is provided inTable 1, and the extrusion conditions employed in this example areprovided in Table 2.

[0038] The physical properties of this monofilament as produced weremeasured according to ASTM D2256-97.

[0039] The shrinkage was tested according to ASTM D204 with thetemperature modified to 204° C. The physical properties of the samplesare outlined in Table 3. Oven aging tests were carried out using aforced air oven maintained at 204° C. (400° F.). Lengths of themonofilaments samples were wrapped into coils approximately 5 cm indiameter. The coils were tied into bundles and placed in the oven,samples being removed at set time intervals. The physical propertyretention was measured as a function of tenacity on an Instron TensileTester. The tenacity retention data is provided in Table 3. TABLE 1Composition of various samples, including samples 1-6 manufacturedfollowing the procedure outlined in Example 1. Con- Sample trol 1 2 3 45 6 PET % PCTA 99.7 98.7 98.7 89.7 89.7 94.7 98.8 % Irganox 0.5 0.5 1010(hindered phenolic) % Nylostab 0.5 S-EED (hindered amine) % Doverphos0.5 0.5 0.5 S-9228 (phosphite) % tri-phenyl phosphate % Polyamide 6 10 %Polyamide 10 6, 6 % Polyamide 10 4 Terpolymer % MB50-004 0.3 0.3 0.3 0.30.3 0.3 0.3 UHMW Silicone Staboxol I 1.2

[0040] TABLE 2 Extrusion and Draw conditions employed in themanufacturing of the samples 1-6. Sample Control 1 2 3 4 5 6 ExtruderTemperature Profile (C.) Throat <60 <60 <60 <60 <60 <60 <60 Feed Zone280 280 280 280 280 280 280 Zone 2 285 285 285 285 285 285 285 Zone 3290 290 290 290 290 290 290 Zone 4 290 290 290 290 290 290 290 Zone 5285 285 285 285 285 285 285 Zone 6 275 275 275 275 275 275 275 Adaptor285 285 285 285 285 285 285 Die 275 275 275 275 275 275 275 ExtrusionConditions Extruder Pressure 1000 1000 1000 1000 1000 1000 1000 (psi)Die Pressure (psi) 720 530 635 1030 750 600 680 Torque (M.g.) 2500 25002000 2500 2500 1900 2200 Screw Speed (rpm) 16 17 17 16 17 17 17 DrawingConditions Total Draw Ration 3.33 3.33 3.33 3.33 3.33 3.33 3.33 DrawOven Temperatures (F.) Oven 1 300 300 300 300 300 300 300 Oven 2 380 380380 380 380 380 380 Oven 3 430 430 430 430 430 430 430

[0041] TABLE 3 Physical property results for the manufactured samples1-6. Sample Control 1 2 3 4 5 6 PET Denier 3450 3492 3534 3326 3492 34623432 2486 Elongation @ Break 33 30 34 30 26 30 30 35 (%) Tenacity (g/d)Initial 2.24 2.22 2.2 2.18 2.21 1.83 1.83 3.8  24 hrs. Failed 2.22 1.721.36 1.43 1.57  39 hrs. 2.22 1.03 1.34 1.43 1.18  45 hrs. 2.22 1.03 0.961.36 1.3  65 hrs. 2.08 Failed Failed Failed 1.05 1.83 2.5  89 hrs. 1.561.05 1.72 2.51 113 hrs. Failed Failed 1.45 2.52

[0042] The control referred to in Tables 1 to 3 is PCTA as described inU.S. Pat. No. 5,981,062. Sample 6 is in accordance with the presentinvention.

[0043] Table 3 clearly shows that sample 5, manufactured using thepolyamide terpolymer provides higher tenacity retention compared toeither of the homopolymers PA6, or PA6,6 used in samples 3 and 4respectively. In addition, comparison of samples 1, 5 and 6 illustratesthe improvement found by combining the polyamide terpolymer and theanti-oxidants in a single blend.

[0044] Comparison of samples 1 and 2 shows the advantages of a hinderedphenolic based anti-oxidant over a hindered amine, ensuring that this isthe preferred primary anti-oxidant. By comparing samples 5 and 6 it isclear that the quantity of polyamide terpolymer used in the blend can besignificantly reduced by utilizing a suitable combination ofanti-oxidants. This provides advantages in processing, as the problemsdescribed herein associated with blending these two polymers arediminished significantly. This will be further illustrated in a laterexample.

[0045] A further embodiment of the present invention is the extension ofthe thermo-oxidative stability of the polyesters described herein suchthat they are comparable to the industry standard PET yarns. The dataindicates that sample 6, which exemplifies the present invention retains80% of its original tenacity after 113 hours at 204° C., whilst PET onlyretains 66% of its original tenacity following the same test period.

EXAMPLE 2

[0046] TABLE 4 Composition of samples 7-12, manufactured following theprocedure outlined in Example 2 including extrusion and draw conditions.Sample 7 8 9 10 11 12 Composition % PCTA 98.8 95.8 91.8 91.8 91.85 91.85Irganox 1010 0.5 0.5 0.5 0.6 0.6 Doverphos S-9228 0.5 0.5 0.5 0.6Di-stearyl thiadi-propionate 0.6 Polyamide 6 4 Polyamide Terpolymar 43.35 3.75 Lubricant 0.4 Color 2 2 2 2 2 Staboxol I 1.2 1.2 1.2 1.2 1.21.2 Extruder Profile (F.) Zone 1 100 100 100 100 100 100 Zone 2 500 500560 560 560 560 Zone 3 560 560 590 590 570 570 Zone 4 560 560 600 600580 580 Zone 5 515 515 530 530 530 530 Zone 6 575 575 580 580 580 580Zone 7 560 560 540 540 540 540 Zone 8 560 560 540 540 540 540 Zone 9 560560 430 430 530 530 Zone 10 560 560 530 530 530 530 Zone 11 550 550 530530 530 530 Adaptor 550 550 560 560 560 560 Head temperature setting 556556 560 560 560 560 Extrusion Conditions Die temperature setting 518 518560 560 560 560 Extruder Pressure (psi) 850 850 1000 1000 1000 1000Extruder Speed (rpm) 125 125 140 140 125 125 Drawing Conditions TotalDraw Ratio 3.43 3.43 3.43 3.43 3.43 3.43 Oven 1 300 300 300 300 300 300Oven 2 320 320 300 300 310 310 Oven 3 330 330 290 290 280 280

[0047] TABLE 5 Physical property results for samples 7-12. Sample 7 8 910 11 12 PET Tenacity (g/den) 2.6 2.5 2.4 2.6 2.4 2.5 3.8 Elongation @20 20 20 21 19 20 35 Break (%) Shrinkage @ 13 12.5 14 13 2 140° C. (%)Hydrolysis Resistance Test Tenacity Retention 0 0 2.16 1.51 2.27 1.62 0After 24 hrs @ 170° C. Steam (g/den) Oven-aging Test Tenacity Retention0 1.7 1.94 1.92 2.16 2.15 2.5 After 89 hrs @ 204° C. (g/den) TenacityRetention 0 0 0 1.19 1.94 1.73 1.63 After 137 hrs @ 204° C. (g/den)

[0048] Samples 10, 11 and 12 are in accordance with the presentinvention.

[0049] In a further example of the present invention, samples of theblends were manufactured using a 147 mm co-rotating and intermeshingtwin screw extruder. The PCTA resin was dried at 260° F. for six hours,the blend components being metered into the polyester using agravimetric, blending system. The composition was fed into the extrudersuch that the rate of feeding could be controlled. Table 4 provides thecompositions and extrusion conditions for the samples. An organicpigment in the form of a masterbatch in a polymeric carrier resin wasadded to the samples to facilitate observation of filament defects.Table 5 outlines the physical properties, and summarizes the hydrolysisresistance and oven aging tests. FIGS. 1 and 2 illustrate theperformance of the best of these blends relative to PET.

[0050] Hydrolysis resistance was measured by placing monofilamentsamples, wrapped into coils of approximately 5 cm diameter, in apressure vessel or autoclave. The tests were performed at 170° C. (7.6atm steam pressure), and 120° C. (1.96 atm steam pressure). The tenacityretention was measured according to ASTMD2256-97. Oven aging tests werecarried out at 175° C. and 204° C.

[0051] Comparing samples 7 and 8 it can be clearly seen that theanti-oxidants improve the resistance to oxidation in the oven-agingtest. Sample 10, incorporating the polyamide terpolymer, hassignificantly better oxidative stability than sample 9, that utilizespolyamide 6. The combination of stabilizers used in sample 11 providesthe best performance, illustrating that by using a combination ofstabilizers, it was possible to reduce the level of the polyamideterpolymer and improve the resistance to the industry standard PET.

[0052]FIG. 1 provides a comparison of the hydrolytic stability of sample12 and PET, tested at 120° C. (1 atm). Clearly the new compositionprovides significantly improved property retention over the industrystandard PET.

[0053]FIG. 2 illustrates the tenacity retention of sample 12 through theoven-aging test at 175° C., with comparison to the industry standardPET. It is evident that this composition has better property retentionat elevated temperatures than the industry standard PET.

EXAMPLE 3

[0054] TABLE 6 Composition of samples 13 and 14, manufactured followingthe procedure outlined in Example 3 including experimental data. Sample13 14 Composition % PCTA 90.1 91.85 Irganox 1010 0.2 0.6 DoverphosS-9928 0.2 0.6 Polyamide Homopolymer 4 Polyamide Terpolymer 3.75Lubricant 1 Color 3 2 Staboxol I 1.5 1.2 Extrusion Pressure Range 200 50Variation (+/−) Diameter Variation (%) 1.5 0.7 Filament AnomaliesPresent None

[0055] Sample 14 is in accordance with the invention.

[0056] In this example, two samples were once again manufactured using a147 mm co-rotating and intermeshing twin screw extruder according to themethod outlined in example 2. The compositions, processing data andphysical appearance measurements are provided in Table 6. The extruderpressure variation was plotted against time for each of the samples andthe data is presented as the maximum pressure range observed during theproduction of the samples. The diameter was measured using a laserscanner, commercially available from Lazermike. The data is expressed asthe maximum % range of the diameters measured during the production ofthe filaments. The scan rate, and dwell time on each filament was keptconstant.

[0057] By switching from polyamide homopolymer to a terpolymer, andoptimizing amount of anti-oxidants added to the composition, thepressure variation was reduced by a factor of 4. One consequence of thispressure reduction is an improvement in the consistency of the filamentsderived. This is clearly illustrated by the improvement in diametervariation when comparing samples 13 and 14.

[0058] The filament anomalies may be defined as short term diametervariation, what are termed “slubs” by those versed in the art, and otherareas of non-uniform structure expressed as short term color variation.Modification of the composition by using less polyamide, and suitableanti-oxidants at optimized addition levels eliminates the anomaliesfound in filaments extruded from blends of polyamide homopolymer andPCTA.

[0059] It is to be understood that the above described examples are byway of illustration only. Many modifications and variations arepossible.

[0060] While this invention has been described as having a preferreddesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A polyester composition, comprising: at least onepolyester derived from a condensation of a 1,4-cyclohexane di-methanoland at least one of a dicarboxylic acid and an ester of saiddicarboxylic acid, said polyester composition between approximately 90%to 97% by weight of said at least one polyester; at least one primaryanti-oxidant defined as at least one of an alkyl and an alkyl peroxyradical scavenger, said polyester composition between approximately 0.1%to 5% by weight of said at least one primary anti-oxidant; at least onesecondary anti-oxidant defined as a compound capable of decomposing ahydroperoxide, said polyester composition between approximately 0.1% to5% by weight of said at least one secondary anti-oxidant; and at leastone polyamide terpolymer, said polyester composition betweenapproximately 1% to 4% by weight of said at least one polyamideterpolymer.
 2. The polyester composition of claim 1, further includingat least one hydrolysis stabilizer, said polyester composition betweenapproximately 0.5% to 2% by weight of said at least one hydrolysisstabilizer.
 3. The polyester composition of claim 1, wherein said atleast one polyester includes a condensation product of a 1,4-cyclohexanedi-methanol and at least one of a terephthalic acid and an esterderivative of said terephthalic acid.
 4. The polyester composition ofclaim 3, wherein said at least one polyester includes a condensationproduct of a 1,4-cyclohexane di-methanol terephthalic and at least oneof a isophthalic acid and an ester derivative of said isophthalic acid.5. The polyester composition of claim 1, wherein said at least oneprimary anti-oxidant includes a hindered phenolic compound.
 6. Thepolyester composition of claim 1, wherein said at least one secondaryanti-oxidant includes a phosphite.
 7. The polyester composition of claim2, wherein said at least on hydrolysis stabilizer includes at least oneof a monomeric carbodiimide and a polymeric carbodiimide.
 8. Thepolyester composition of claim 1, further including a polyamideterpolymer stabilizer having a melting point between approximately 120°to 220°.
 9. The polyester composition of claim 8, wherein said polyamideterpolymer stabilizer includes a copolymer of three different amiderepeat units.
 10. A monofilament, comprising: at least one of a yarn anda fiber, said at least one of a yarn and a fiber including a polyestercomposition having: at least one polyester derived from a condensationof a 1,4-cyclohexane di-methanol and at least one of a dicarboxylic acidand an ester of said dicarboxylic acid, said polyester compositionbetween approximately 90% to 97% by weight of said at least onepolyester; at least one primary anti-oxidant defined as at least one ofan alkyl and an alkyl peroxy radical scavenger, said polyestercomposition between approximately 0.1% to 5% by weight of said at leastone primary anti-oxidant; at least one secondary anti-oxidant defined asa compound capable of decomposing a hydroperoxide, said polyestercomposition between approximately 0.1% to 5% by weight of said at leastone secondary anti-oxidant; and at least one polyamide terpolymer, saidpolyester composition between approximately 1% to 4% by weight of saidat least one polyamide terpolymer.
 11. A papermachine clothing,comprising: at least one monofilament having at least one of a yarn anda fiber, said at least one of a yarn and a fiber including a polyestercomposition having: at least one polyester derived from a condensationof a 1,4-cyclohexane di-methanol and at least one of a dicarboxylic acidand an ester of said dicarboxylic acid, said polyester compositionbetween approximately 90% to 97% by weight of said at least onepolyester; at least one primary anti-oxidant defined as at least one ofan alkyl and an alkyl peroxy radical scavenger, said polyestercomposition between approximately 0.1% to 5% by weight of said at leastone primary anti-oxidant; at least one secondary anti-oxidant defined asa compound capable of decomposing a hydroperoxide, said polyestercomposition between approximately 0.1% to 5% by weight of said at leastone secondary anti-oxidant; and at least one polyamide terpolymer, saidpolyester composition between approximately 1% to 4% by weight of saidat least one polyamide terpolymer.
 12. A papermachine clothing,comprising: a polyester composition having: at least one polyesterderived from a condensation of a 1,4-cyclohexane di-methanol and atleast one of a dicarboxylic acid and an ester of said dicarboxylic acid,said polyester composition between approximately 90% to 97% by weight ofsaid at least one polyester; at least one primary anti-oxidant definedas at least one of an alkyl and an alkyl peroxy radical scavenger, saidpolyester composition between approximately 0.1% to 5% by weight of saidat least one primary anti-oxidant; at least one secondary anti-oxidantdefined as a compound capable of decomposing a hydroperoxide, saidpolyester composition between approximately 0.1% to 5% by weight of saidat least one secondary anti-oxidant; and at least one polyamideterpolymer, said polyester composition between approximately 1% to 4% byweight of said at least one polyamide terpolymer.